10:45 AM - 12:15 PM
[SMP26-P08] Flow properties of peridotite in the uppermost mantle explored from the Hayachine-Miyamori ultramafic body
Keywords:Olivine CPO, Hayachine-Miyamori ophiolite, Subduction zone, Back-arc, Uppermost mantle
The Hayachine-Miyamori ophiolite is a complex formed in a subduction zone during the Ordovician (Ozawa, 1988; Ozawa et al., 2015). It is characterized by especially hydrous minerals such as hornblende and phlogopite, and is an excellent target to discuss the influence of water in subduction zones. In this study, field survey, microstructural observations, crystal orientation analysis, and compositional analysis of major mineral elements of peridotites in the Hayachine-Miyamori ophiolite were performed in order to clarify the flow properties of the uppermost mantle. The mantle section of the Hayachine-Miyamori ophiolite has been divided into an aluminous spinel ultramafic suite (ASUS) and a chromite-bearing ultramafic suite (CRUS) depending on mineral chemical features. The Hayachine complex is mostly composed of ASUS, while the Miyamori complex is mainly CRUS with patchy domains of ASUS. Petrologically and geochemically, the Hayachine and Miyamori bodies are characterized as back-arc and fore-arc, respectively (Ozawa, 1984,1988,2001; Ozawa & Shimizu, 1995; Yoshikawa & Ozawa, 2007).
We sampled some peridotites within ASUS from the Hayachine complex as well as CRUS from the Miyamori complex and subsequently prepared their polished thin sections. Crystallographic preferred orientations (CPOs) of olivine have been classified into six types: A-type with (010)[100] slip system, B-type with (010)[001] slip system, C-type with (100)[001] slip system, D-type with {0kl}[100] slip system, E-type with (001)[100] slip system and AG-type that is difficult to identify the slip systems. Our samples showed various major constituent minerals and microstructures. Most of the CPOs were A-type or AG-type as reported by Ozawa (1989), whereas E-type has been found in a peridotite in the Hayachine complex. The E-type peridotite contains hornblende, which appears to be classified into ASUS.
In this study, we discuss flow properties of peridotites found in both the ASUS of the Hayachine complex and the CRUS of the Miyamori complex.
We sampled some peridotites within ASUS from the Hayachine complex as well as CRUS from the Miyamori complex and subsequently prepared their polished thin sections. Crystallographic preferred orientations (CPOs) of olivine have been classified into six types: A-type with (010)[100] slip system, B-type with (010)[001] slip system, C-type with (100)[001] slip system, D-type with {0kl}[100] slip system, E-type with (001)[100] slip system and AG-type that is difficult to identify the slip systems. Our samples showed various major constituent minerals and microstructures. Most of the CPOs were A-type or AG-type as reported by Ozawa (1989), whereas E-type has been found in a peridotite in the Hayachine complex. The E-type peridotite contains hornblende, which appears to be classified into ASUS.
In this study, we discuss flow properties of peridotites found in both the ASUS of the Hayachine complex and the CRUS of the Miyamori complex.